Wife just called and said "a square orange light just came on on the upper left side of the dash." I can't visualize the dash warning lights and trying to figure out which one it is. Battery, coolant?

Without knowing the year of your truck, I'm assuming that it is a 2000 or newer and has a message center on the left side of the of the instrument panel.

If it was an orange square, with no writing in it, then it was probably the Battery warning light, which illuminates when there is a problem with the charging system. The engine coolant light would more than likely be a message that says TEMP, and the check engine light would be shaped like an engine (both would be in the message center).

Battery warning indicator.

It is hard to say, it could have just been a glinch if it has not came back on again.